The ABCD-USA Consortium proposes a study designed to permit our investigators and the scientific community to answer important questions about the effects of substance use (SU) on behavioral and brain development of adolescents. We have assembled a team of investigators with unparalleled research experience with youth, and specific expertise in adolescent SU, child and adolescent development, developmental psychopathology, longitudinal multi-site imaging, developmental neuroimaging and cognitive neuroscience, genetics and imaging genetics, bioassays, epidemiology, survey research, bioinformatics, and mobile assessment technologies. We propose a nationwide study of 10,000 9-10 year olds conducted at 21 sites organized into 11 hubs (29% of the US population lives within 50 miles of our geographically spread sites), that, uniquely, can provide a nationally representative sample and a large twin sample that together can help distinguish environmental, sociocultural, and genetic factors relevant to SU and brain development. We ensure cohesion and standardization with a recruitment strategy designed by a professional survey company (experience with Monitoring the Future); standardized environmental, neurocognitive and mental health assessments, MRI assessments with scanners using harmonized Human Connectome Project procedures, and computerized data collection with real-time quality control. Developmentally tailored assessments will have stable sensitivity and construct validity across childhood and adolescence, minimize participant burden, capture even subtle changes in SU, mental health, neurocognition, development, and environment, and employ novel bioassays and passive data collection from mobile devices. The retention plan builds on the experience of our investigators to ensure success. This application describes the ABCD-USA Coordinating Center (CC) which will: provide overall administrative and logistical support and scientific integration fr the consortium; establish and implement procedures for core protocols, participant recruitment and retention, and data quality control; provide initial and ongoing training of personnel for standardization; monitor cohort attributes, recruiting and retention practices, data quality, and consortium-wide consistency in real time, and monitor progress toward benchmarks and timelines. CC will ensure adherence to ethical standards and cultural sensitivity of research, and establish and implement policies for dispute resolution, internal and external data sharing, and publication. CC organizes and provides logistical support for meetings and teleconferences of the consortium, steering committee, scientific advisory board and workgroups as well as for educational, scientific, outreach, and dissemination events. By design, CC processes are flexible for problem resolution and incorporation of emerging scientific opportunities. We provide transparent study updates to the public via the web, and a well-managed and fully annotated repository of data for timely sharing. Importantly, we provide training and mentoring to developing scientists in the drug abuse area.